This application claims priority from Japanese application No. 2000-140797, which is hereby incorporated by reference into this application.
1. Field of the Invention
The invention relates to a horn switch arranged on a steering wheel for vehicles. More specifically, the invention relates to a horn switch provided with a connecting bolt, by which a movable member being depressed is connected to a stationary member to enable operation of the horn switch.
2. Description of Related Art
Conventionally, a horn switch of this kind is known as described in Japanese Patent Laid-Open No. 106382/1998 and the like. The horn switch disclosed in the above-mentioned publication comprises a stationary member supported on a steering wheel body and a movable member connected to a horn pad. The stationary member includes a stationary contact. The movable member includes a movable contact adapted to touch with the stationary contact to enable actuating a horn. The movable member is arranged above the stationary member.
A spring is arranged between the stationary member and the movable member to bias the movable contact away from the stationary contact. Also, a connecting bolt is arranged between the stationary member and the movable member to connect the movable member to the stationary member. The connecting bolt is arranged to allow downward movement of the movable member and to prescribe a distance of the movable contact from the stationary contact. The connecting bolt comprises a head and a shank extending upward from the head. The head is adapted to abut against an underside of the stationary member. The shank is fastened to a threaded hole in the movable member.
However, such a conventional connecting bolt is designed to extend through the stationary member from below the stationary member to be fastened to the movable member. Therefore, there is the possibility of the connecting bolt falling if it becomes loose.
Also, at the time of fastening of the connecting bolt, the stationary member and the movable member must be positioned so as not to deviate from each other. After such positioning, the connecting bolt is inserted through the stationary member to be fastened to the threaded hole in the movable member. Therefore, it is conventional that a plurality of positioning holes are provided around the threaded hole on the movable member and positioning projections provided on the stationary member are fitted into the positioning holes, thus facilitating fastening of the connecting bolt to the movable member.
A plurality of such connecting bolts are arranged at fastening locations on the entire steering wheel and rotated to be fastened to the movable member. Therefore, the movable member is sometimes subjected to rotative torque at the time of fastening a connecting bolt. In this case, the positioning projections get out of the positioning holes at other fastening locations of other connecting bolts to cause positional deviation, which takes time to correct, adding time to the operation of fastening the connecting bolts.
Aspects of the invention address or solve the above-mentioned problems. One aspect of the invention provides a horn switch for a steering wheel which is capable of preventing the falling of a connecting bolt even in the event of its becoming loose, and in which the fastening operation of a connecting bolt is made easier.
These and other aspects of the invention can be attained by providing a horn switch for a steering wheel constituted in the following manner.
A horn switch for a steering wheel comprises a stationary member having a stationary contact and supported on a steering wheel body, and a movable member having a movable contact, which touches the stationary contact to enable actuating a horn, arranged above the stationary member. A spring is arranged between the stationary member and the movable member for biasing the movable contact upward so as to space the same away from the stationary contact. A connecting bolt connects the movable member to the stationary member so as to allow downward movement of the movable member and to prescribe a distance of the movable contact from the stationary contact. The connecting bolt comprises a head abutting against an underside of the stationary member and a shank extending upward from the head to be fastened to a threaded hole in the movable member. The connecting bolt is capable of being temporarily fixed to the stationary member with a lower surface of the head latched and is capable of being fastened to the movable member when temporarily fixed to the stationary member.
With the horn switch according to the invention, the connecting bolt is temporarily fixed to the stationary member before tightening. Therefore, a lower surface of the head is latched even if the connecting bolt becomes loose, thus eliminating the possibility of its falling.
Of course, when being fastened to the movable member, the connecting bolt is only temporarily fixed to the stationary member with the lower surface of the head being latched. At this time, the shank extending from the head extends toward the threaded hole of the movable member. Therefore, the shank of the connecting bolt is fitted into the threaded hole only by mounting a jig, such as a driver or the like, on the head of the connecting bolt and pushing and turning the same. As a result, the connecting bolt can be fastened to the movable member without trouble.
Accordingly, with a horn switch for a steering wheel according to the invention, the falling of a connecting bolt can be prevented even in the event of its becoming loose, and the fastening operation of a connecting bolt can be made with ease.
Also, with the above-mentioned horn switch, it is preferable that the stationary member comprises a stationary base connected to the steering wheel body and a stationary support member connected to the stationary base for supporting the stationary contact. The stationary support member preferably comprises a joint portion capable of joining to a mount hole of the stationary base. The stationary support member is formed with latch legs, which project below an underside of the stationary base when the joint portion is joined with the mount hole, being capable of temporarily fixing the connecting bolt.
With the horn switch thus constituted, the latch legs provided on the stationary support member being capable of temporarily fixing the connecting bolt are mounted on the stationary base by joining a joint portion of the stationary support member, which supports the stationary contact, to a mount hole of the stationary base. Accordingly, mounting of other members for temporarily fixing the connecting bolt to the stationary member is dispensed with. As a result, it is possible to reduce the number of constituent parts for the horn switch and man-hours for assembly.
Further, with the above-mentioned horn switch, it is preferable that the movable member comprises a movable base connected to a pad, which is depressed to enable operation of the horn switch, and has a threaded hole, and a movable support member connected to the movable base to support the movable contact, By this arrangement, the stationary contact, the movable contact, the stationary support member, the movable support member and the spring are formed to have a substantially cylindrical shape provided with an insertion hole, which permits the shank of the connecting bolt to be inserted therethrough. The stationary support member and the movable support member, which support the stationary contact and the movable contact, respectively, are constructed to engage with each other to enable a switch assembly to be formed in a state in which they interpose the spring therebetween and allow downward movement of the movable support member.
With the horn switch thus constituted, the switch assembly can be formed in a state in which the stationary support member and the movable support member, which support the stationary contact and the movable contact, respectively, are made to engage with each other with the spring interposed therebetween. At this time, the engagement is effected in a state in which the movable support member is allowed to move downward. Therefore, it is possible to handle the stationary and movable contacts, the stationary and movable support members, and the spring without losing them, which is convenient in handling, such as during mounting to the stationary base thereafter. And the stationary and movable contacts, the stationary and movable supporting members and the spring, which constitute the switch assembly, are formed to have a substantially cylindrical shape provided with an insertion hole. The insertion hole permits the shank of the connecting bolt to be inserted therethrough. Therefore, there is no possibility of interfering with the connecting bolt, which is to be temporarily fixed to the stationary member.
Further, with the horn switch described above, a cover portion is preferably formed on either of the stationary support member and the movable support member to be capable of covering an area surrounding the contact portions at which the stationary contact and the movable contact touch each other in operation of the horn switch.
With the horn switch thus constituted, the cover portion provided on either of the stationary support member and the movable support member covers an area surrounding the contact portions at which the stationary contact and the movable contact touch each other in operation of the horn switch. Therefore, foreign matters can be prevented from entering between the contact portions, at which the stationary contact and the movable contact touch each other in operation of the horn switch.
Further, with the horn switch described above, it is preferable that the threaded hole formed on the movable base is formed with a tapered guide surface at a peripheral edge of a lower end thereof.
With the horn switch thus constituted, threading of the male thread portion is facilitated when the connecting bolt is fastened to the threaded hole. Therefore, it is possible to improve work efficiency in mounting of the horn switch.
Further, with the horn switch described above, it is preferable that the shank of the connecting bolt comprises a male thread portion formed at an upper end thereof to be capable of threading into the threaded hole, and a large-diameter portion formed at a lower end thereof to be larger in outer diameter than the male thread portion. The connecting bolt is adapted to be threaded into the threaded hole with a washer, which has the same outer diameter as that of the large-diameter portion, between the large-diameter portion and the movable member.
With the horn switch thus constituted, when the connecting bolt is to be fastened to the threaded hole, they interpose therebetween the washer without interposition of the movable support member and the movable contact, so that the large-diameter portion abuts directly against the movable base. Therefore, there is no possibility of the movable support member and the movable contact being deformed. Of course, it is possible to fasten the connecting bolt to the movable base with the washer therebetween in a state in which fastening forces are enhanced.
Further, with the horn switch described above, it is preferable that the stationary support member and the movable support member are each formed with engagements which cause engagement therebetween. The engagements are preferably formed around the connecting bolt to be disposed in four positions spaced circumferentially uniformly from one another.
With the horn switch thus constituted, the engaging portions at which the stationary support member and the movable support member engage with each other are separated uniformly around the connecting bolt. Therefore, the stationary support member and the movable support member can be stably engaged with each other.
Further, with the horn switch described above, it is preferable that the movable member corrects and supports an airbag device.
With the horn switch thus constituted, the airbag device and the horn switch are beforehand assembled together, and the airbag device and all other parts can be mounted to the steering wheel body making use of the stationary members of the horn switches. Therefore, it becomes easy to assemble the steering wheel body. That is, in the case of directly mounting a small horn switch on a large steering wheel body, the ring section of the steering wheel body creates interference, making assembly difficult. However, in the case of mounting a horn switch on an airbag device smaller than a steering wheel body, there are fewer parts creating interference, thereby making assembly easier. This is because it is easy to find any part or parts which fall.
Further, with the horn switch described above, it is preferable that the movable base is formed integrally with a bag holder, which constitutes the airbag device, and is die-cast.
With the horn switch thus constituted, it becomes unnecessary to arrange on the bag holder any nuts provided with threads for threading of the male threaded portions of the fastening bolts, thus reducing the man-hours required for manufacture of the bag holder and reducing or eliminating costs.